text: The main scientific works of Yusif Mammadaliyev are related to catalytic progressing of oil and Fuel oil. He is the founder of petrochemistry in Azerbaijan. He suggested new methods of chlorination and bromination of different hydrocarbons with participation of catalysts and especially showed the ways of obtaining carbon tetrachloride, chloromethane, dichloromethane and other valuable products by means of chlorination of methane, initially in stationary catalyst, and then in hot layer. Researches in the sphere of catalytic alkylation of aromatic, paraffinic, naphthenes hydrocarbons with the help of unsaturated hydrocarbons, enabled the synthesis of the components of aviation fuels on industrial scale. The major works were executed in the sphere of catalytic aromatization of benzine fraction of Baku oil, obtainment of washing agents, flint-organic compounds, production of plastics from pyrolized products, analysis of Naftalan oil's action mechanism. He repeatedly represented Azerbaijan in congresses, conventions and symposiums held by the USSR, United States, Italy, France, England, Moldavia, Poland and other countries.